1. Field of the Invention
The present invention relates to a communication terminal apparatus connected to an exchange network having an interrupt/restart function, e.g., an ISDN (Integrated Services Digital Network).
2. Description of the Prior Art
In a conventional communication terminal apparatus such as a facsimile apparatus connected to an ISDN, when a scanner, a printer or the like connected (as a connected local device) to the apparatus causes a trouble which disables data communication, e.g., a paper jam, out of paper, or the like, this results in a communication disabled state. In this case, the apparatus sends a communication interrupt designation command to the network (i.e., to an apparatus on the other end of the line). When the trouble is recovered, the apparatus outputs a communication restart designation command to restart communication with the apparatus on the other end of the line. When a communication termination apparatus is moved along one subscriber line during communication, a communication interrupt designation command is sent to the network, and a restart designation command is sent at a destination of movement, so that the terminal apparatus can be moved and communication can be restarted without disconnecting a line.
When a communication apparatus on the other end of the line receives the communication interrupt designation command from the apparatus which caused the trouble or the apparatus which is to be moved, it interrupts communication, and restarts communication when the trouble is recovered or the movement is completed, and the communication restart designation command is received.
However, when the communication terminal apparatus outputs or receives the interrupt/restart designation command, a communication monitoring timer for monitoring an accumulation communication time with the network is kept operated, and the communication monitoring timer continuously accumulates a time between the interrupt and restart designation commands. In this case, there is no problem when the restart designation command is issued soon. However, when a long time interval elapses before the restart designation command is issued, the communication monitoring timer causes a time-out error, and communication is undesirably stopped although communication processing is normally performed.
At this time, it is determined that communication is abnormally ended, resulting in intermediate termination.
Alternatively, the apparatus may immediately stop communication upon reception of the interrupt designation command without monitoring time at the communication monitoring timer.
In the prior art, when a trouble occurs in the connected local device of the communication apparatus, communication is stopped in the middle of communication, resulting in omission of received documents.
Even when the trouble of the local device is recovered, extra processing such as re-connection and re-transmission processing must be performed.